THE smartphone speed war is poised to intensify as Vodafone today announced the country's fastest 4G mobile phone network due to launch in June, outpacing rivals Telstra and Optus.

The smallest of the major telcos will launch its 4G network in all mainland state capitals and three regional centres, and promises speeds that are "up to 15 times faster on average than our current 3G network".

But Vodafone's 20MHz network will be equipped to deliver downloads as fast as 150 megabits per second, a spokeswoman said - 50 megabits per second faster than the top speed on Telstra's 15MHz network.

That top speed could theoretically let users download an album in one second or a high-definition movie in fewer than 30 seconds.

But telecommunications experts say the company, widely dubbed "Vodafail" by disgruntled users, will have to prove its claims before winning new and old customers.

Vodafone chief executive Bill Morrow said the 4G network announcement was part of a larger move to win back consumers' trust and improve services.

"Our customers have said they want faster speeds, more coverage, and a dependable network," he said.

"We are proud to be able to deliver our customers Australia's fastest 4G network in metro areas, backed by a solid 3G+ experience."

Vodafone's 4G network will cover large parts of Sydney and Perth when it launches in June, with coverage in some parts of Melbourne, Adelaide, Brisbane, the Gold Coast, Newcastle and Wollongong.

But, unlike other networks, Vodafone is able to use the widest 4G bandwidth that can deliver faster download speeds than competing networks. Customers must use a Category Four smartphone or USB modem to access faster downloads, however.

Telsyte research director Foad Fadaghi said demand for 4G smartphones and services had been "phenomenal" in Australia and Vodafone needed to announce a 4G network just to compete.

But he said the company should be careful not to promise faster speeds it could not deliver.

"Vodafone have called its 4G network 'potentially the fastest' and that's important," he said.

"There are inherent risks in claiming specific speeds. Nevertheless, it's important for them to have that speed leadership to get back in the market."

Mr Fadaghi said Vodafone could not simply rely on a faster network to win back customers, however, and would also need to announce competitive plans, discounted 4G handsets and prove that its new network was reliable.